3. Materials and Methods The LEA study is based on the constitution of a multi-centric prospective cohort in 11 university hospitals: Bordeaux, Clermont-Ferrand, Grenoble, Lyon, Paris (Trousseau, Robert Debré, St Louis), Marseille, Montpellier, Nancy, Nice, Rennes. Are inclued in LEA all the children diagnosed and treated for acute leukemia since January 1980 (incident and prevalent cases), surviving at month 24 for the AML and ALL grafted in complete remission and at month 48 for the ALL not grafted in first complete remission.